1. Field of the Invention
The present invention relates to an acceleration detector for detecting impact acceleration that exceeds reference acceleration for driving and controlling a vehicle occupant protection system.
2. Description of Related Art
FIG. 19 is a top view showing a vehicle occupant protection system such as an air bag system. In this figure, the reference numeral 1 designates the body of a vehicle; 2 designates an occupant protection system against right-side crashes, which is mounted on the right side in the vehicle in its traveling direction; and 3 designates an occupant protection system against left-side crashes, which is mounted on the left side in the vehicle in its traveling direction.
The reference numeral 4 designates a right-side collision sensor unit for detecting the impact in right side crashes; 5 designates a left-side collision sensor unit for detecting the impact in left side crashes; and 6 designates a controller mounted on the vehicle, for controlling the occupant protection system 2 against the right-side crashes and the occupant protection system 3 against the left-side crashes.
FIG. 20 is a block diagram showing an electrical configuration of the occupant protection system of FIG. 19. In this figure, the reference numeral 11 designates a semiconductor type right-side collision acceleration sensor for producing an electric signal proportional to the acceleration the vehicle undergoes on the right side in its traveling direction; and 12 designates a microcomputer that recognizes the acceleration from the electric signal supplied from the right-side collision acceleration sensor 11, and outputs a control signal for closing a semiconductor switch 19 when the acceleration exceeds impact acceleration (acceleration beyond reference acceleration). Likewise, the reference numeral 13 designates a semiconductor type left-side collision acceleration sensor for producing an electric signal proportional to the acceleration the vehicle undergoes on the left side in its traveling direction; and 14 designates a microcomputer that recognizes the acceleration from the electric signal supplied from the left-side collision acceleration sensor 13, and outputs a control signal for closing a semiconductor switch 20 when the acceleration exceeds the impact acceleration.
The reference numeral 15 designates a power supply; 16 designates a mechanical right-side collision acceleration sensor that is mounted inside a controller 6 for detecting the impact acceleration the vehicle undergoes on the right side in its traveling direction; and 17 designates a mechanical left-side collision acceleration sensor that is mounted inside the controller 6 for detecting the impact acceleration the vehicle undergoes on the left side in its traveling direction. The reference numeral 18 designates a microcomputer that outputs a control signal for closing a semiconductor switch 21 when the right-side collision acceleration sensor 16 detects the impact acceleration, and that outputs a control signal for closing a semiconductor switch 22 when the left-side collision acceleration sensor 17 detects the impact acceleration. Reference numerals 19-22 each designate a semiconductor switch. The reference 23 designates a driving circuit for driving an occupant protection system 24 when the semiconductor switches 19 and 21 are closed; and 24 designates the occupant protection system such as an air bag against the right-side crashes. Likewise, the reference numeral 25 designates a driving circuit for driving an occupant protection system 26 when the semiconductor switches 20 and 22 are closed; and 26 designates the occupant protection system such as an air bag against the left-side crashes.
Next, the operation of the conventional occupant protection system will be described.
For example, when another vehicle collides with the right side in the traveling direction of the vehicle, the right-side collision acceleration sensor 11 supplies the microcomputer 12 with the electric signal proportional to the acceleration applied on the right side of the vehicle. At the same time, the right-side collision acceleration sensor 16 detects the impact acceleration beyond the reference acceleration, and supplies the detection signal to the microcomputer 18.
Receiving electric signal from the right-side collision acceleration sensor 11, the microcomputer 12 recognizes the acceleration from the electric signal, and when the acceleration exceeds the impact acceleration, it recognizes the right side collision, and outputs the control signal to close the semiconductor switch 19.
Likewise, receiving the detection signal from the right-side collision acceleration sensor 16, the microcomputer 18 recognizes the right side collision, and outputs the control signal to close the semiconductor switch 21.
Thus, the power supply 15 supplies a current to the driving circuit 23 through the semiconductor switches 19 and 21, so that the driving circuit 23 drives the occupant protection system 24 against the right-side crashes.
On the other hand, when another vehicle collides with the left side in the traveling direction of the vehicle, the left-side collision acceleration sensor 13 supplies the microcomputer 14 with the electric signal proportional to the acceleration applied on the left side of the vehicle. In addition, the left-side collision acceleration sensor 17 detects the impact acceleration beyond the reference acceleration, and supplies the detection signal to the microcomputer 18.
Receiving electric signal from the left-side collision acceleration sensor 13, the microcomputer 14 recognizes the acceleration from the electric signal, and when the acceleration exceeds the impact acceleration, it recognizes the left side collision, and outputs the control signal to close the semiconductor switch 20.
Likewise, receiving the detection signal from the left-side collision acceleration sensor 17, the microcomputer 18 recognizes the left side collision, and outputs the control signal to close the semiconductor switch 22.
Thus, the power supply 15 supplies a current to the driving circuit 25 through the semiconductor switches 20 and 22, so that the driving circuit 25 drives the occupant protection system 26 against the left-side crashes.
FIG. 21 is a plan view showing a conventional acceleration detector (right-side collision acceleration sensor 16 or left-side collision acceleration sensor 17) disclosed in Japanese patent application laid-open No. 9-211023/1997, for example. In this figure, the reference numeral 31 designates a weight; 32 designates a shaft on which the weight 31 slides when the weight 31 undergoes an inertial force by the crash of the vehicle; 33 designates a spring; 34 designates a moving contact; and 35 designates a fixed contact.
As clearly shown in FIG. 21, the conventional acceleration detector has its fixed contact 35 and moving contact 34 separated apart in a normal mode where no collision takes place.
If the weight 31 undergoes a large inertial force beyond the force of the spring 33 by the collision of the vehicle, it moves to the left in FIG. 21, so that the moving contact 34 comes into contact with the fixed contact 35.
Thus, when the fixed contact 35 makes contact with the moving contact 34, the acceleration detector 16 or 17 supplies the detection signal to the microcomputer 18.
With the foregoing arrangement, it is necessary for the conventional acceleration detector 16 or 17 to have the fixed contact 35 and moving contact 34 disposed in such a manner that they are spaced by a rather large distance so that they do not come to contact with each other in the normal mode. The rather large distance between the fixed contact 35 and moving contact 34 offers a problem of reducing the response sensitivity to the impact acceleration.
In addition, it has another problem in that the detection direction of the impact acceleration is limited to one direction.
The present invention is implemented to solve the foregoing problems. It is therefore an object of the present invention to provide an acceleration detector capable of improving the response sensitivity to the impact acceleration.
Another object of the present invention is to provide an acceleration detector capable of detecting the impact acceleration bidirectionally.
According to a first aspect of the present invention, there is provided an acceleration detector including a mass member making contact with a fixed contact; and an elastic member that presses the mass member to the fixed contact, wherein when the mass member moves toward the elastic member by an inertial force exceeding a pushing force of the elastic member, a conducting state between the mass member and the fixed contact is broken. Thus, it offers an advantage of being able to improve the response sensitivity to the impact acceleration.
Here, the fixed contact may include a plurality of fixed contacts, and the mass member may be composed of a conductive material, wherein when the mass member moves toward the elastic member, a conducting state between the plurality of fixed contacts may be broken. Thus, it offers an advantage of being able to improve the response sensitivity to the impact acceleration, without increasing the complexity in structure and the number of components.
The fixed contact, the mass member, and a fixed member may be arranged in this order, and the mass member may be composed of a conductive material, wherein when the mass member moves toward the elastic member, a conducting state between the fixed contact and the fixed member may be broken.
According to a second aspect of the present invention, there is provided an acceleration detector including; first and second mass members making contact with first and second fixed contacts, respectively; and an elastic member that presses these mass members to the first and second fixed contacts, wherein when at least one of the mass members moves toward the elastic member by an inertial force exceeding a pushing force of the elastic member, the mass member that moves breaks its contact with one of the fixed contacts that kept contact with it. Thus, it offers an advantage of being able to improve the response sensitivity to the impact acceleration, and to detect the impact acceleration in both directions.
Here, the first and second mass members may be composed of a conductive material, wherein when at least one of them moves toward the elastic member, the conducting state between the two fixed contacts may be broken. Thus, it offers an advantage of being able to improve the response sensitivity to the impact acceleration, without increasing the complexity in structure and the number of components.
At least one of the fixed contacts may be composed of a plurality of fixed contacts. This makes it possible to detect an abnormal input such as radio noise, thereby offering an advantage of being able to prevent erroneous driving of the occupant protection system.
The mass member may consist of a part of the elastic member. This offers an advantage of being able to increase the efficiency of the assembly, and to fabricate the acceleration detector at lower cost.
The first and second mass members may make contact with each other before the elastic member reaches its elastic yield point. This offers an advantage of being able to increase the reliability of the acceleration detector.
At least one of the fixed contacts may have an elastic structure that alters its shape in response to the pushing force of the elastic member. Thus, the acceleration detector can prevent unexpected disconnection by large, short impact acceleration such as hammering, thereby offering an advantage of being able to achieve stable operation.
The first and second mass members may have different inertial masses. This enables the acceleration detector to be mounted at various places on the vehicle.
When a non-conducting state between the mass member and the fixed contact is detected, the acceleration detector may drive an occupant protection system. This offers an advantage of being able to protect the occupants at a crash.
The mass member may be allowed to move when the vehicle undergoes side-to-side acceleration. This offers an advantage of being able to detect a side collision.
Thee mass member may be allowed to move when the vehicle undergoes back-and-forth acceleration. This offers an advantage of being able to detect a frontal or rear collision.